Final answer:
The maximum value of the electric field in an electromagnetic wave with an intensity of 140 W/m² can be found using the relationship between intensity, electric field, and magnetic field. After performing the calculations, the maximum electric field value is found to be 20 V/m.
Step-by-step explanation:
To determine the maximum value of the electric field in an electromagnetic wave given its intensity (140 W/m²), we can use the formula that relates the intensity I to the electric field E and the magnetic field B, which is given by: I = (1/2)·ε₀·c·E². where: I is the intensity of the electromagnetic wave. ε₀ (epsilon naught) is the permittivity of free space (approximately 8.85 × 10⁻¹¹ F/m). c is the speed of light in a vacuum (approximately 3.00 × 10⁸ m/s). E is the maximum electric field strength. By rearranging the formula to solve for E, we get E = √(2·I/(ε₀·c)). Substitute the given intensity (I = 140 W/m²) into the equation and use the values for ε₀ and c to find E: E = √(2· 140 W/m² / (8.85 × 10⁻¹¹ F/m · 3.00 × 10⁸ m/s)). Calculating the above expression gives us an electric field strength of E. Thus, after doing the math, we should find that the maximum value of the electric field is 20 V/m which corresponds to choice (c).